A new index for land surface inhomogeneity and its impact on sensible heat flux measured by Large Aperture Scintillometer (LAS) over eastern Gansu of Loess Plateau

Abstract

There are few quantitative researches focused on the influence of inhomogeneous land surface condition on sensible heat fluxes measured by Large Aperture Scintillometer (LAS) and Eddy Covariance System (ECS) at present. In this paper, based on the observed land surface process data in two prevailing wind directions (E-SE and SW-W) at Qingyang site in the Loess Plateau during June and July 2012, firstly, a quantitative index representing the degree of land surface inhomogeneity was established, and then an analysis was made of the relationship between surface inhomogeneity and surface temperature variability and its influence on the difference between LAS and ECS measured sensible heat fluxes. Results showed that the land surface inhomogeneity eta had a good correlation with surface temperature variability (sic) with a correlation coefficient up to 0. 566, indicating that eta can well represent land surface inhomogeneity. eta also had a good consistency with the difference between LAS and ECS measured sensible heat fluxes (H-LAS-H-ECS), its correlation coefficient being up to 0. 634. eta significantly influenced the difference between LAS and ECS measured sensible heat fluxes. The more inhomogeneous 77 was, the greater H-LAS-H-ECS was. For the two prevailing wind directions, eta had a correlation coefficient of 0. 430 with H-LAS-H-ECS in E-SE wind direction, the fitting coefficient being 1. 279; eta had a correlation coefficient of 0. 680 with H-LAS-H-ECS in SW-W wind direction, the fitting coefficient being 1. 297. LAS and ECS measured sensible heat fluxes will have a greater difference when the influence of land surface inhomogeneity is larger.